Many organizations, including commercial on-line information services and corporate networks, maintain directories of users that can be accessed by other users. In a corporate network, a user may access the directory by looking up a name or an extension number; and in a directory for a commercial service, a user may use a name or a name with other information to obtain records.
With such on-line directories, a user who is searching for information about another user can enter a request that has a name and, in some directories, other keywords, such as a city, profession, or hobby. In response, the directory provides one or more records of users that match the request. These records may have certain minimum required information, or may have other information that other users choose to provide.
If a user wants to send an email message to an intended recipient, the user may be able to get the recipient's email address from such a directory. The user can then compose and send an email message to the recipient. If the email address is not provided to the directory by the user, or if the directory does not have such a field, the user cannot obtain the email address. If email addresses are provided to and then by the directory, users risk receiving unwanted email and having their email addresses sent to others.